1. Field of the Invention
This invention relates to the fabrication of semi-conductor devices. Particularly, the present invention relates to a method for consistently preparing high efficiency tin oxide-silicon heterojunction solar cells and indium tin oxide-silicon heterojunction solar cells by deposition of the appropriate oxide from vapor state on N-type silicon.
2. Prior Art
There has been considerable interest in recent years directed toward the development of semiconductive heterojunction devices comprising an electrically conducting transparent window material deposited on a semiconductive substrate. Such interest is based on the potential that such devices can be fabricated at lower costs than homojunction devices based on the conventional diffusion of N and/or P materials into silicon. Additionally, heterojunction conducting oxide devices offer the added advantage that the transparent window permits the transmission of solar radiation directly to the active substrate with little or no attenuation. One such type of heterojunction solar cell proposed is a tin oxide-silicon heterojunction solar cell.
A very early report on a tin oxide-silicon heterostructure solar cell by Kajiyama and Furukawa, Japan Journal Applied Physics, 6, p. 905 (1967) indicated that such a cell had sunlight conversion efficiency of about 0.1%. More recently, however, Franz et al, Journal of Electronic Materials, Vol. 6, No. 2, pp. 107-123 (1977) reported measured sunlight conversion efficiencies for tin oxide-silicon solar cells of close to 10%. Subsequently, Anderson reported to the National Science Foundation, Report NSF/RANN/SE/AER67-04168/PR/77/1,2 (July 1977) that attempts to repeat the previously high sunlight conversion efficiency reported by him, Franz and his coworkers in J. Elec. Mat., supra, for the tin oxide-silicon heterojunction solar cells have been unsuccessful.
Accordingly, it is one of the principal objects of the present invention to provide a method for fabricating high efficiency tin oxide-silicon heterojunction solar cells.